Data from several cancer screening studies are being collected and analyzed to gain a better understanding of the impact and consequences of such screening in various population settings, and to develop new techniques for data analysis. Section staff are involved in various aspects of these studies, including design, monitoring, and data analysis. Screening Section investigators collaborated with the Early Detection Branch and the Research Contracts Branch in developing the major components of the PLCO Trial. This is a major trial of cancer screening in males and females for four cancers that comprise more than 50% of the incidence and mortality of cancer: lung, prostate, colorectal, and ovarian cancers. The trial design calls for a total sample size of 74,000 males and 74,000 females between the ages of 60 and 74 who are to be divided at random into a screened group and a control group. The screening techniques to be used are annual digital rectal examination and prostate specific antigen for prostate cancer, annual chest film for lung cancer, annual digital rectal examination and three-year flexible sigmoidoscopy for colorectal cancer, and annual pelvic examination plus CA-125 marker and transvaginal ultrasound for ovarian cancer. Contracts for the coordinating center, screening centers, and laboratory were developed and a draft protocol was written. Initiation of the pilot phase of the trial is planned for early 1993. The database from the HIP breast cancer screening trial was used to address several scientific and modeling issues. Issues under investigation included the magnitude and duration of benefit, age-specific effectiveness, and application to model development. Data from the NCI sponsored lung cancer screening trials were analyzed. Investigations included assessment of incidence and mortality information. Monitoring continued of a trial to evaluate testing for blood in the stool for the early detection of colorectal cancer. Evaluation of screening for neuroblastoma in infants was addressed in conjunction with investigators at the University of Minnesota. Staff consulted in a controlled study to assess the measurement of urinary catecholamine metabolites VMA and HVA as screening tests for this tumor. Staff were also involved in the design of two new screening initiatives. One is a study to evaluate screening for stomach cancer in a high risk population in Costa Rica by testing for pepsinogen in the blood. The other is a study to be conducted in the People's Republic of China aimed at assessing cytology, endoscopic ultrasonography and other tests for esophageal cancer.